mail.catobe.pl has no CNAME records.
Question and response
Question
dig mail.catobe.pl. NS
Answer
The response has no answer records.
Authority
catobe.pl. 1361 SOA jeff.ns.cloudflare.com. dns.cloudflare.com. 2397055401 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0